In prefabricated buildings, essentially two types of roof supporting structures are currently employed. The first type of supporting structure is the rafter-purlin system which utilizes essentially linear or one-way structural members. The problem with using one-way purlins or joists is instability in the lateral direction. This problem requires the extensive use of bracing members between the purlins or joists, which adds materially to the cost of the building, particularly since the bracing members must be individually installed on the job site after the one-way structural members have been put in place.
The second type of load supporting structure is composed of three-dimensional interlocking trusses which form a grid structure. Such structures are usually constructed in place on the job site by assembling a large number of three-dimensional units into a complete grid system. While structures of this type are quite strong, they are also expensive due to the labor needed to fabricate and erect the individual units into a complete grid structure.
In contrast to the foregoing, the present invention contemplates a roof system utilizing individual load supporting truss units which are self-bracing and have a high capacity for both vertical and lateral loading, the units being readily assembled on the job site and installed with a minimum of labor. While primarily intended as load supporting units in a roof, the truss units of the present invention also may be used as structural members for supporting flooring, wall girts and the like.